Joe Lewis has not caused this much of a stir since he teamed up with a pack of speculators, including George Soros, to bet on the pound crashing out of the European exchange rate mechanism - which it did 15 years ago this Sunday.

Black Wednesday, in 1992, cost the Treasury an estimated £3.4bn and generated fortunes for the Bahamas-based currency trader and the others. Some even maintain the rags-to-riches British tax exile scooped more than Soros.

Now Lewis, who is best known in the UK for having taken interests in Tottenham Hotspur and Rangers, has resurfaced at another pivotal moment. In the midst of a global credit crisis, he has snatched a major stake in Bear Stearns, one of Wall Street's "big five" investment banks. Its shares have lost more than a quarter of their value since May because of the bank's exposure to high-risk mortgage loans in the US, known as sub-prime mortgages.

The £425m stake has thrown an unwelcome spotlight on the wider business activities of 70-year-old Lewis. Will he look to seize control of Bear? Is he a white knight riding to the rescue, or a corporate raider looking to make a quick turn? Lewis, who conducts operations from his Bahamas mansion - with currency trading screens in almost every room - is giving nothing away.

"He doesn't like to talk to people," his daughter Vivienne once explained. "It aggravates him." Aware of the value he puts on his privacy, few within the currency trading world will talk openly about Lewis, known to many as the Boxer after his near-namesake, heavyweight champion Joe Louis.

In a rare interview nine years ago, he told the New York Times: "One of the rewards of your success is the quiet enjoyment of it. Being on the front page of newspapers doesn't allow that."

That quiet determination, however, has served him well. "You don't get to be a wise old guy in the FX [foreign exchange] market without being a real shrewdie," said one senior City figure who used to do business with him. "Not many can survive that long."

Lewis, who retains something of his Cockney accent, was born above the Roman Arms pub in Bow, in the heart of London's East End, and left school at 15 to help run Tavistock Banqueting, his father's West End catering business, starting out as a waiter.

For a time, it hosted a lot of masonic functions before expanding in the 70s to target American tourists, laying on a high-kitsch "medieval banqueting" experience. Also working for Tavistock was Robert Earl, who, with Lewis's backing, later went on to develop the themed restaurant idea into the Hard Rock Café and Planet Hollywood franchises.

Entrepreneurial zeal made Lewis a multimillionaire when he sold the family catering business in 1979, relocating to the Bahamas. But instead of resting on his laurels, he reinvented himself as a currency trader and made hugely successful bets not only against the pound in 1992, but also against the Mexican peso three years later. It was these jackpots that signalled to the world that Lewis was a lot more than a retired British leisure magnate lazing in the sun.

Quite how he developed such trading aptitude is not clear, but testimony to his powers can be found in the fortunes amassed by his many proteges. They include the Monaco-based Englishman Michael Tabor as well as Irishmen JP McManus, Dermot Desmond and John Magnier - best known as former Manchester United investors.

Outside the currency world, Lewis's fortune is put to work through Tavistock Group, a private equity business named after his father's catering firm and run out of his second home, a mansion in a Florida gated community which is itself another Lewis investment.

Lewis's total wealth is impossible to assess, particularly his fortune from currency trading. He was named the richest man in Britain in the mid-90s (despite his tax exile status), and estimates this year put his fortune at £2.8bn.

In the UK his chief lieutenant is Daniel Levy, best known as the controversial chairman at Tottenham Hotspur. Levy, the son of the Mr Byrite discount clothing chain founder, has used his sponsor's backing to build a name in the City, pursuing some well-timed investments. Other not-so-successful investments include aborted attempts to take over Christie's, the auction house, Victor Chandler, the offshore bookmaker, and Wembley stadium.

There has always been media interest around the football investments but Lewis has shown little interest in the sport. His preference is for tennis, sailing and golf, where he sponsors the Tavistock Cup. His golfing friends include Tiger Woods - whom he once partnered after paying £1.4m at a charity auction for the privilege - Ernie Els and fellow tax exile Sean Connery.

Lewis remains fit, playing off a handicap of 12 or 13. He is said, on occasion, to leave his younger executives breathless as he hops from fairway to tennis court.

The CV

Born February 5 1937, over his father's pub, the Roman Arms, in Bow, east London. His father, Charles, was in the restaurant and catering industry.

Family Lives in £15m house in Bahamas with second wife Jane, his former assistant. Has two children from first marriage to Esther Browne.

Home Divides time between Bahamas and estates in Florida and Argentina.

Career Left school at 15 to work in his father's business, which he quickly expanded to form the Hanover Grand restaurant and banqueting group. Relocated to the Bahamas as a tax exile in 1979, moving into foreign exchange dealing and stock market investing. His Florida-based Tavistock Group oversees a portfolio of investments in 170 companies in more than 15 countries.